paper

An atomistic insight into moiré reconstruction in Twisted Bilayer Graphene beyond the magic angle

arXiv:2301.01310 · doi:10.1021/acsaenm.2c00259

Abstract

Twisted bilayer graphene exhibits electronic properties that are highly correlated with the size and arrangement of moiré patterns. While rigid rotation of two layers creates the topology of moiré patterns, local rearrangements of the atoms due to interlayer van der Waals interactions result in atomic reconstruction within the moiré cells. The ability to manipulate these patterns by controlling twist angle and/or externally applied strain provides a promising route to tune their properties. While this phenomenon has been extensively studied for angles close to or smaller than the magic angle (θm=1.1°), its extent for higher angles and how it evolves with strain is unknown and is believed to be mostly absent at high angles. We use theoretical and numerical analyses to resolve reconstruction in angles above θm using interpretive and fundamental physical measures. In addition, we propose a method to identify local regions within moiré cells and track their evolution with strain for a range of representative high twist angles. Our results show that reconstruction is actively present beyond the magic angle and its contribution to the evolution of the moiré cells is major. Our theoretical method to correlate local and global phonon behavior provides further validation on the role of reconstruction at higher angles. Our findings provide a better understanding of moiré reconstruction in large twist angles and the evolution of moiré cells in the presence of strain, that might be very crucial for twistronics-based applications.

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